The present invention relates to a test plug and method for isolating and pressure testing a connection between a tank, vessel, or pipe and a nozzle or branch pipe extending externally therefrom.
Site specifications, applicable design codes, and/or applicable testing codes typically require testing of new or modified piping, tank, and/or vessel systems including the testing of connections made between all piping components. The testing can be, for instance, a positive pressure test or a vacuum test and must verify the structural integrity of the system and determine if any leaks exist within the system, particularly at pipe connection locations. U.S. Pat. No. 5,797,431 issued to Adams, which is assigned to EST Group Inc., the assignee of present application, and U.S. Pat. No. 5,024,079 issued to Dufort disclose examples of known test plugs.
The Adams patent discloses a test plug which is used to seal a non-flanged end of a pipe. To this end, the test plug is inserted into the open end of a pipe and expanded to grip and form a fluid-tight seal with an inner peripheral surface of the pipe. Thus, the pipe can be pressure tested downstream of the inner diameter test plug while the test plug provides a fluid-tight seal and prevents the plug from being blown out of the pipe during high test pressure conditions.
The Dufort patent discloses a test plug for a flanged pipe in which an expandable distal end of the plug is inserted into the pipe and an opposite flanged end of the plug is connected to a flanged-end of a pipe to create a fluid-tight seal. For instance, see FIGS. 4-6 of the Dufort patent. When the distal end is expanded, it also creates a fluid-tight seal so that the weld between the pipe and the flange of the pipe can be pressure tested. To this end, fluid is injected into the flanged end of the plug and only the flanged end of the pipe is tested so that the remaining piping system is not required to be placed under pressure during the pressure testing of the flange connection.
While the above referenced test plugs function satisfactorily for their intended purposes, they cannot be utilized to isolate and test a connection, such as a welded connection, between a tank, vessel, or pipe and a branch pipe or nozzle, without having to pressurize the entire tank or vessel or a large portion of the piping system. For example, FIGS. 1A-1C of the present application illustrates a section 10 of a hollow, cylindrical, relatively large diameter pipe, tank or vessel and an externally-extending, relatively smaller diameter, flanged branch connection 12. The flanged branch connection 12 can be, for instance, a relatively smaller diameter branch pipe or tank nozzle. An interior weld location 14 or an exterior weld location 16 can be utilized, for example, to join the flanged branch connection 12 to section 10. The relative diameters of section 10 and branch connection 12 can vary widely and are not required to have a circular transverse cross-section, as illustrated.
In the construction of such systems as shown in FIGS. 1A-1C, inlets, outlets, welded fittings, nozzle connections and branch line connections 12 are made transversely through the periphery of the relatively larger diameter pipe, vessel or tank section 10. As best shown in FIGS. 1B and 1C, an inner end 18 of the branch connection 12 typically extends entirely within the larger diameter pipe, tank or vessel section 10. The opposite end 20 of the branch connection 12 can be connected by a weld 22 to a flanged end 24 as illustrated in FIGS. 1A-1C, or can be without a flange end as best illustrated in FIG. 8 of the present application as will be discussed in greater detail. Typically, if such systems are made from steel components, the connections are made utilizing welding techniques; however, other known techniques can also be utilized to join the various components. As stated above, typically the various components are cylindrical, however, the various joined components can have, for instance, rectangular, square, spherical, or oval transverse cross sections.
Conventionally, pressure testing of the internal or external welds 14 or 16 of the branch connection 12 to section 10 is accomplished by pressurizing the entire piping system, tank or vessel, or a large part of the piping system. Thus, such testing is time consuming, expensive, and can create potential hazards. In addition, welding operations utilized to join a branch connection 12 to an existing section 10 of a piping system, tank or vessel may be performed in the presence of combustible, dangerous, and/or otherwise harmful materials or vapors which are present within the existing piping system, tank or vessel. Thus, the welding operation as well as the testing operation may be subject to potential hazards.
Various patents disclose pipe, tank, or vessel testing or repair apparatus and methods. For example, U.S. Pat. No. 5,760,296 issued to Wilson discloses the use of an inflatable bladder to form a fluid-tight seal with an inner wall of a vessel adjacent a nozzle. The bladder is inserted through an opening in the nozzle and is positioned within the vessel before being inflated. The disclosed pressure testing device is designed to isolate the vessel from the nozzle so that the vessel can be pressure tested, not the vessel-to-nozzle weld connection.
U.S. Pat. No. 5,996,401 issued to Lewis discloses a leak test adaptor system that attaches to a vessel via a test port and permits the vessel to be filled with a tracer gas or fluid so that the vessel and the test port can be simultaneously tested for leaks. A plug is located within the test port and is manipulated between sealing and non-sealing positions by a rod which extends externally of the vessel. Thus, an adaptor can be connected to the test port to open the plug, fill the vessel with a tracer gas, and close the plug to test for leaks.
U.S. Pat. No. 5,331,841 issued to Beaver et al. discloses a process and apparatus for repairing a damaged surface of a nozzle extending from a vessel. To this end, a new inner nozzle is installed within the damaged nozzle to line the damaged nozzle, and a seal is formed at both ends of the new inner nozzle to create a leak-free repaired nozzle. As illustrated in FIG. 8 of the Beaver patent, a gasket can be utilized to form a seal between the inner wall of the tank and the end of the new nozzle inserted within the tank.
U.S. Pat. No. 6,131,441 issued to Berube et al. and U.S. Pat. No. 4,890,843 issued to Vetter disclose other devices for isolating and testing pipe segments.
Although the test plugs and methods of isolating and testing pipe sections and/or tanks and vessels disclosed in the above referenced patents may function satisfactorily for their intended purposes, there remains a need for a test plug device and method which enables ready isolation and testing of a connection, such as a welded connection, between a tank, vessel, or pipe and a branch pipe or nozzle. Preferably, the test plug should isolate the connection from the tank, vessel or remaining piping system to enable testing of the connection without requiring the entire tank or vessel or a large section of the piping system to be pressurized. In addition, preferably the test plug should isolate a welding operation from harmful materials or vapors existing within the tank, vessel or piping system and should permit an inert gas to be utilized to flush any potentially harmful vapors or the like away from the area to be welded. Further, the test plug and method should permit reliable, ready and efficient installation and use requiring only a minimum of skill and labor, and the test plug should be inexpensive to manufacture.
With the foregoing in mind, a primary object of the present invention is to provide a test plug which enables ready isolation and testing of a connection, such as a welded connection, between a tank, vessel, or pipe and a branch pipe or nozzle.
Another object of the present invention is to provide a test plug which isolates the connection from the tank, vessel or remaining piping system to enable pressure/leak testing of the connection without requiring the entire tank or vessel or a large section of the piping system to be subject to the test pressurization.
A further object of the present invention is to provide a test plug which isolates welding operations utilized to connect branch connections to tanks, vessels or pipes from harmful materials or vapors existing within the tank, vessel or piping systems and which permits the flow of an inert gas to flush any potentially harmful vapors or the like away from the area to be welded.
A still further object of the present invention is to provide a method which is used to isolate and test a branch connection and which permits reliable, ready and efficient installation requiring only a minimum of skill and labor.
More specifically, the present invention is a test plug for isolating and testing the integrity of a connection, such as a welded connection, between a wall of a vessel, such as a tank or pipe, and a relatively smaller branch pipe, such as a nozzle, which extends transversely therefrom. The branch pipe typically has an inner end extending within the vessel and an open free end extending externally of the vessel. The test plug includes an inner subassembly that encloses the inner end of the branch pipe and forms a fluid-tight seal with an inner surface of the wall of the vessel adjacent and surrounding the connection when the test plug is in an installed condition. The test plug also includes a second subassembly for forming a fluid-tight seal with the opposite free end of the branch pipe. When installed, the inner and second subassemblies interact to form a fluid-tight chamber that isolates the connection from a remainder of the vessel. This enables the chamber to isolate the connection from vapor and materials present within the vessel and to be utilized to perform high pressure integrity and leak tests of the connection.
The inner subassembly of the test plug has an end surface which mates with the inner surface of the wall of the vessel surrounding the connection when the test plug is installed. Preferably, the end surface of the inner subassembly is contoured to substantially correspond to a contour of the inner surface of the wall of the vessel to ensure the formation of a proper seal.
According to another aspect of the present invention, a method is provided for isolating and proving the integrity of a connection between a wall of a vessel and a relatively smaller branch pipe extending transversely therefrom. The method includes inserting at least a portion of a test plug through the branch pipe and enclosing an inner end of the branch pipe that extends within the vessel with an inner subassembly of the test plug. The inner subassembly extends around the inner end of the branch pipe to an inner surface of the wall of the vessel adjacent and surrounding the connection. The test plug forms a fluid-tight seal adjacent an open free end of the branch pipe which extends externally of the vessel, and upon tightening of the test plug, the inner subassembly of the test plug forms a fluid tight seal with the inner surface of the wall of the vessel adjacent and surrounding the connection. This results in the formation of a fluid-tight chamber that extends only within the branch pipe and around and closely spaced to the inner end of the branch pipe. The fluid-tight chamber is completely isolated from a remaining portion of the vessel and can be utilized to pressure test the connection.